belief revision

The area of theory change in which
preservation of the information in the theory to be changed
plays a key role.

A fundamental issue in belief revision is how to decide what
information to retract in order to maintain consistency, when
the addition of a new belief to a theory would make it
inconsistent. Usually, an ordering on the sentences of the
theory is used to determine priorities among sentences, so
that those with lower priority can be retracted. This
ordering can be difficult to generate and maintain.